Washing after intercourse does not prevent pregnancy. This is due to the fact that the sperm enters the woman’s uterine cavity through the cervix immediately after the man ejaculates, and when the woman washes, some of the sperm has already entered the uterine cavity and pregnancy may occur. In addition, a woman’s vagina has many folds and washing does not rinse out all the semen inside the vagina, which can also lead to pregnancy in this case. If a woman does not want to get pregnant, she must take efficient contraceptive measures. She can use condoms before intercourse or take short-acting contraceptive pills after her period, which are more reliable.